I had tried the free Google Desktop at work, twice, and each time uninstalled it. First because I could not search my network drives. (I like to use network drives to share files with my colleagues, and to make sure they are backed up.) Later I had decided to try again, and then discovered the possible security issues.
I was pleasantly surprised to learn that Google now has addressed the security concerns and they have released an update that will index networked drives. I have been running this now for about two weeks, and it generally has performed well. The Google Desktop Search is based on keywords, so it does not always give you the most relevant results. I also had some troubles with PowerPoint running very slow while editing. (I turn the search off when I am working in PowerPoint.) With those caveats, it seems to be a good solution.
A nice, new feature is that if you hit your CTRL button twice, a search dialog appears in the center of your screen. Of course Google Desktop will provide many more gadgets and garbage when you install it, so you need to pay close attention to make sure you disable those functions. But if you are looking for a good search across network drives at a low cost (free), I recommend giving Google Desktop another look.